Currently solutions for Massive Machine Type Communication (M-MTC) are being standardized within 3rd Generation Partnership Project (3GPP). These solutions include NarrowBand Internet of Things (NB-IoT) and Long Term Evolution (LTE) Cat-M (“Category Machines”). They are both targeting similar use cases with extreme battery lifetime, support for large coverage and inexpensive terminal chipsets.
A typical use case is a communication device in the form of e.g. a power meter located in a basement outside normal cellular coverage. Hence, many of the devices are expected to be stationary. Also, for the majority of the devices in a network, the coverage condition is quite good and bit rates of around 100 kbps can be achieved. For exceptional cases, devices located in areas suffering from extremely limited coverage conditions, e.g. deep underground or in basements, the data rate can be scaled down to enhance the coverage.
For both NB-IoT and LTE Cat-M it can be expensive to schedule Channel Quality Indication (CQI) reports, and for extended coverage mode in Cat-M the support for CQI reports has even been removed. Since IoT devices can experience very high path loss in downlink, reception quality can be heavily impacted by interference from neighboring cells.
However, without explicit channel feedback (i.e. CQI or similar) from the device there is no way to know how much this interference affects reception quality. This means that it will be impossible for a base station serving the device to track changes in downlink interference. Ultimately, this means that link adaptation for the downlink may be too aggressive resulting in periods of time when downlink block error rate can be very high.